1. Field of the Invention
This invention relates to single lens reflex cameras in which a reflex mirror has a light-permeable portion for splitting part of light coming from an object to be photographed and entering through the objective lens into the light meter, and more particularly to a light shielding device for the aforesaid light-permeable portion.
2. Description of the Prior Art
In the past it has been known to provide a single lens reflex camera in which the reflex mirror for reflecting light fron the objective lens to the penta prism is provided with a light-permeable portion so that when the reflex mirror is in the viewing position, light from the light-permeable portion is received by a light sensor for automatic detection of the distance from the camera to the object and derivation of a light value based on which the exposure operation of the camera is determined. Also in such camera it is known to cover the light-permeable portion by a shutter plate when the reflex mirror moves to the exposing position, as is, for example, disclosed in Japanese Laid-Open Patent No. Sho 56-12626 (published on Feb. 7, 1981).
Incidentally, in such camera, use is made of a stopper on which the shutter plate abuts when the reflex mirror has moved to the exposing position. In the case where the opening and closing operation of the shutter plate is controlled by this stopper, certain problems arise.
When the reflex mirror is moved from the viewing to the exposing position by a mirror operating mechanism, the upper dead point of the reflex mirror (the nearest point of the mirror to the exposing position) differs from camera to camera because of the existence of variations in size and relative position of parts of the mirror operating mechanism. In some of the items, therefore, it happens that with the reflex mirror is moved to the exposing position, the shutter plate cannot perfectly cover the light-permeable portion. Because of this, there exists a drawback that during the exposure operation of the camera, light from the finder eye-piece enters through the light-permeable portion to reach the film surface with the result that incorrect exposure occurs.
Also in case the opening and closing of the shutter plate is controlled by a rigid stopper, since the stopper absorbs the kinetic energy of the reflex mirror in a very short time as it moves from the viewing position to the exposing position, the kinetic energy is converted to sonic energy, heat energy and work energy, and in large proportion to sonic energy and work energy. This phenomena, causes the sound at the time of collision to become very loud, and the stopper and the shutter plate are substantially worn.